Abstract

Background

While it is known that advanced age alters the recruitment of neutrophils during wound
healing, thereby delaying the wound healing process, little is known about prolonged
wound healing in advanced ages. Thus, we investigated the correlation of neutrophil
recruitment with healing events, and the impact of whey protein (WP) on neutrophil
activation.

Methods

The animals were allocated into wounded young group, wounded older group and wounded
older rats with daily treatment of WP at a dose of 100 mg/kg of body weight.

Results

Our results pointed to a marked deficiency in the number of neutrophils in the wounds
of older rats, which was accompanied with impairment of the healing process. In the
group of older rats, phagocytic activity, as tested by fluorescence microscopy, declined
throughout the first 24 hours after wounding. Both the neutrophil number and the phagocytic
activity recovered in older rats which received WP supplementation. Interestingly,
WP was found to significantly up-regulate the MIP-1α and CINC-1 mRNA expression in
old rats. On the other hand, the wound size in older rats was significantly higher
than that in younger ones. Blood angiogenesis was also significantly delayed in the
older group as opposed to the young rats. WP, however, was found to return these indices
to normal levels in the older rats. Proliferation and epidermal migration of the keratinocytes
and the collagen deposition were also returned to the normal rates.

Conclusions

This data confirms the critical role of neutrophil recruitment in the early inflammatory
phase of wound healing in older rats. In addition, WP protein was used to improve
neutrophil function in older rats, healing events returned to a more normal profile.